Described below is a method for laser melting, in which a component is produced in layers in a bed of powder, in that the particles forming the bed of powder are melted by at least one working laser beam. When they solidify, the particles then form a layer of the component. Subsequently, successive further layers of powder particles are formed on the solidified area of the component and are in turn melted by the working laser beam. This produces a three-dimensional component layer by layer.
Methods of the type specified at the beginning are known. One problem concerning the implementation of such methods is the high rate of cooling that occurs when cooling the molten pool produced in the powder by the laser beam. This typically leads to the formation of a very fine-grained microstructure, which, depending on the application, does not bring about the desired mechanical component properties. In particular, the elongation at break and the creep resistance may be reduced. In order subsequently to achieve a desired range of properties of the component produced, a heat treatment may be carried out, with the result of making the grains coarser. However, such a heat treatment cannot be carried out in the case of all materials. Furthermore, this heat treatment means that there is additional expenditure in terms of energy and production, whereby the cost-effectiveness of the components produced suffers.
In addition to the working laser beam, which produces the energy input for melting the molten pool, it is possible according to DE 10 2010 050 531 A1 and DE 10 2010 048 335 A1 to use at least one auxiliary laser beam of which the power density is too low to bring about melting of the particles. This at least one auxiliary laser beam is directed onto a cooling zone following the molten pool and lying on the component. The energy input brought about by the auxiliary laser beam is therefore not sufficient to melt the particles. This also means, however, that the auxiliary laser beam cannot keep the particles in the molten state. Rather, a cooling of the molten pool, and also of the cooling zone lying on the component, can be noted, but the auxiliary laser beam reduces the cooling rate, and consequently the temperature gradient in the cooling component.
The method improves laser melting to the extent that more favorable component properties with regard to the mechanical characteristic values can be produced.